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The effect of a modified cell structure in the gate region on the electrical characteristics of three-dimensional (3D) NAND flash memory devices was investigated by using a technology computeraided design simulation. The interference in the memory devices induced by the pass voltage (Vpass) interference of 3D NAND flash was significantly affected depending on the cell size. The Vpass memory device with a modified cell structure was reduced due to an increase in the electron density of the inversion layer in comparison with conventional 3D flash memory devices, and their program operation was enhanced by the increased electric field. Furthermore, the program/erase margin of the proposed 3D NAND flash memory device was 15% larger than that of the conventional 3D NAND flash memory device.

Choi, J.U.; Lee, Y.G.; Jeong, D.U.; Choi, Y.H., and Woo, H.J., 2018. Effects of Abalone Farming Cage Removal on the Benthic Foraminiferal Assemblages. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 321–325. Coconut Creek (Florida), ISSN 0749-0208. To improve the aquaculture environment of an abalone farm near the Bogil Island, relocation was executed via the partial relocation of cages. The surface sediments were collected from nine stations to analyze the grain size, geochemical characteristics, and benthic foraminiferal assemblages in May (before) and August (after) 2015. Although no distinct environmental changes in the cage area were observed, the relocation area had an increased sand content caused by water circulation. In addition, despite the increase in the sediment temperature, the ignition loss decreased while the dissolved oxygen in the se...

The objective of this study was to examine gonad development and reproductive cycle of the abalone Haliotis discus hannai at three main abalone aquaculture farms (Uljin, Wando, and Jeju Island) in Korea to obtain information on artificial seed production. The sex ratio (female:male) was approximately 1:1 without significant difference among the three regions or between females and males. Average gonad index was the highest during July in Uljin and Jeju Island and during August in Wando. There was no definitive seasonal change in condition index and meat weight index throughout the year in the three regions. The gonad of H. discus hannai displayed seasonal change histologically, thereby enabling us to distinguish the following stages: inactive (November–December), early active (January–March), late active (March–April), ripe (May–July), spent (August–October), and degenerative (October–November). The main spawning period of H. discus hannai was determined to be during September–October in Uljin and Wando, and August–September in Jeju Island.

Tidal current survey as well as geochemical and benthic foraminiferal analyses of sediment cores were conducted in an abalone farm and a Zostera bed to understand the degree to which the abalone farm facilities installed along a channel in a shallow sea affect the benthic environment and ecology. In the abalone farm, Ammonia beccarii-Pseudoparrella naraensis-Elphidium somaense-Rosalina globularis-Trochammina hadai and P. naraensis-E. somaense-A. beccarii-T. hadai assemblages appeared owing to an increase in the total nitrogen content from the biodeposits. The Zostera bed consisted of A. beccarii-P. naraensis-Buccella frigida-T. hadai assemblage owing to the gradual expansion of a brackish shallow-water environment by the rapidly decreasing current speed, and it may have flourished. Moreover, the total sulfur, Zn, Cr, and Cu contents in the sediments decreased remarkably more than those of the pre-abalone farming did, caused by the vigorous activity of Zostera marina physiology.

Analyses of the compositions of benthic foraminifera and sediment, observations of tidal level and salinity, and a geographic survey of the tidal salt marsh in Suncheon Bay were conducted to examine the vertical distribution of foraminifera and evaluate their potential use for sea level studies. The salt marsh is composed mainly of fine-grained silty clay sediment and its salinity is below approximately 11 psu. The tidal current flows in the southwest-tonortheast direction with an average velocity of 26.57 cm/s. A total of 33 species of foraminifera (17 agglutinated and 16 calcareoushyaline) belonging to 24 genera was identified. The species diversity (1.1 on average) was relatively low. Dominant species were Ammonia beccarii, Miliammina fusca, Haplophragmoides wilberti, and Jadammina macrescens. Calcareous foraminifera (29.5%) were dominantly represented by the Ammonia beccarii assemblage, which characterized the region between mean tide level and mean low high water (MLHW). Agglutinated species (70.5%) were represented mostly by Miliammina fusca, Miliammina fusca-Haplophragmoides wilberti, and Haplophragmoides wilberti assemblages, which characterized the MLHW–mean high water (MHW), MHW–mean highest high water (MHHW), and MHHW–Approx. highest high water tide levels, respectively. In particular, the Haplophragmoides wilberti assemblage is believed to represent the highest elevation zone of foraminifera in the salt marshes of Suncheon Bay and is considered to be a reliable indicator of sea level as a result of its narrow vertical range.

Jeong, D.U.; Lee, Y.G.; Kang, J.; Woo, H.J., and Choi, Y.H., 2020. Sediment geochemistry and benthic foraminiferal response to fish farming after conversion from a red laver (seaweed) farm. Journal of Coastal Research, 36(3), 559–574. Coconut Creek (Florida), ISSN 0749-0208.To understand the effects of biodeposits discharged from a fish farm (which was previously a red laver farm) on geochemistry of the sediment and benthic ecology, trace metals and element analyses, 210Pb dating, and benthic foraminiferal analyses were conducted on sediment cores collected below the fish farm cages. Sediment core sampling was also carried out at a control plot (160 m away) to understand the spreading of biodeposits. The geochemical effect of fish farming is pronounced. There was an increase in silt content and sedimentation fluxes of Znex (Zn in excess fractions), Cuex, Asex, and TPex (total phosphorus in excess fractions) after red laver farming. The silt content increased from 45.01% to 50.07%, with a sediment accumulation rate of ∼0.61 cm/y, on average. TPex, with 0.15% ± 0.06% on average, showed that the fish farming effects increased by 0.22% ± 0.07%. Znex, Cuex, Cdex, and Asex showed a positive relationship with TPex increase: 19.92 ± 1.79, 10.23 ± 3.99, 0.57 ± 0.19, and 0.92 ± 0.04 µg/cm2/y, respectively. The high sedimentation fluxes of Znex and Asex in the control plot may signify an expansion of influence of the fish farm by tidal currents. Seven benthic foraminifera appeared during the fish and red laver farming periods, with the dominant species being Cribroelphidium excavatum; however, they were characterized by a high similarity index of 88.1% and very low frequency of abundance, indicating bad habitat conditions. Among them, the C. excavatum–Ammonia beccarii–Ammonia ketienziensis–Cribroelphidium subarcticum assemblage ranged from 21 cm depth to the uppermost layer, characterized by increases in A. beccarii. This increase may have been caused by the accumulation of organic matter discharged from the fish farm after red laver farming, rather than from an increase in the trace metals. A. beccarii may be a species tolerant to fish farming.

Lake Shihwa suffers from trace-metal pollution discharged from the Banweol stream and the Shihwa Industrial Complex. Installation of floodgates in 2001 increased water exchange and decreased trace-metal content, thereby improving the benthic environment within the lake. We analyzed surface sediments (including grain size, pH, trace-metal concentrations), water-quality data, and the assemblages of, and prevalence of deformities in, the benthic foraminifera, to understand the effects of recent changes in salinity variability. Since spatial and temporal distributions of benthic foraminifera are known to vary in response to both biotic and abiotic environmental variables, they are useful indicators of environmental change. Since the installation of floodgates, surface-sediment composition coarsened from silt to sandy mud/muddy sand in response to increased water flow. Trace-metal contaminants (Ni, Cu and Zn) have decreased and are close to the Effect Range-Low (ER-L) designation. We identified 15 species of benthic foraminifera (3 agglutinated, 10 calcareous-hyaline, and 2 calcareous-porcelaneous). Buccella frigida and Elphidium albiumbilicatum were dominant, but seven sampling localities formed a nearly abiotic zone. Although trace contaminants have decreased, a high prevalence of test deformities (up to 65%) was observed, mostly in E. albiumbilicatum . Our findings suggest these abnormalities may be strongly related to the effects of seasonal variation of salinity in Lake Shihwa.

In order to determine the effects on foraminifera due to spilled crude oil in the "Herbei Spirit" incident, a study of benthic foraminiferal assemblages was carried out on sediment samples collected from the Sogeunri tidal flat, Taean Peninsula, Korea. Breakages of the chambers in the Ammonia beccarii and Elphidium subincertum species of the Sogeunri tidal flat with a low pH (6.98 on average) were marked. These chamber breakages occurred in 71.6% of A. beccarii and are thought to be caused by decalcification due to the fall in pH resulting from the "Hebei Spirit" oil spill. The factors that affect breakage of the chamber in benthic foraminifera under low pH condition may be not only deto decalcification but also to exposure duration of substrata in the tidal flat spilled crude oil.

Choi, Y.H.; Jeong, D.U.; Lee, Y.G.; Choi, J.U.; Kim, S., and Lee, J.S., 2019. Opportunistic species and seasonal variation in epiphytic foraminiferal assemblages in abalone farm nets. Jour...

This study investigated concentration of metal ions in sediment and intersexuality in Polymesoda erosa and Lutraria lutraria . Samples were collected from five areas of Ha Long Bay in October, 2012. The concentration of metal ions showed that Al (37390.0 ± 11816.5 mg/kg) was highest and Mn (360.4 ± 101.4 mg/kg) was second high concentration. Cd (0.04 ± 0.05 mg/kg) was lowest. The intersexuality was 14.3% in P. erosa and 9.1% in L. lutraria that observed only in female. Key words: Ha Long Bay, bivalves, heavy metal, intersexuality 서 론 수서생태계에서 생물에게 미치는 화학적 스트레스 요인 가운데 중금속은 생물 체내 축적성이 강하고 대사, 생화학, 생리학 및 조직학적 반응의 변화를 유도한다 (Stasiūnaitė, 1999). 중금속 가운데 Cd, Pb, Hg, Zn은 생식 등의 내분비계 장애기능을 유발하는 기능을 가지고 있다 (WWF, 2006; Ju et al ., 2009). 해양의 중금속은 퇴적물과 쉽게 결합하며, 해수보다 퇴적물에 매우 높은 농도로 분포한다 (Martin and Whitifield, 1983). 이매패류는 주로 해양저질에 서식하며, 여과섭식을 하며 이동성이 낮아 일생동안 서식범위가 국한되어 있어서 특정 지역의 오염상태를 알아보기 위한 지표종으로 많이 사용되고 있다 (Marin et al ., 2006; Schintu et al ., 2008; Husmann et al ., 2012). 환경요인으로 인해 생물이 받는 위해도를 평가하는 방법은 위험성 확인 (hazard identification), 노출평가 (exposure assessment), 용량-반응 평가 (dose-response assessment) 및 위해도 결정 (risk characterization) 의 주요 4단계이다 (NRC, 1983). 다양한 생물지표 가운데 생식생물학 및 조직학적 지표들은 개체 또는 개체군 수준에서 독성물질에 의한 장기적이고 지속적인 영향을 평가하는데 중요하게 이용되는 항목이다 (Huggett

The rate of sex reversal in the Manila clam Ruditapes philippinarum was 19.0%. The male to female sex reversal ratio was 21.1%, which was higher than the female to male sex reversal ratio of 12.9%. Based on our results, R. philippinarum is confirmed to be a sequential hermaphrodite.

This study was performed to obtain information on the sex ratio, size at sexual maturity, and main spawning period of the butter clam Saxidomus purpuratus in Korea to contribute to the management of fisheries resources of this species. The age-specific sex ratios (female:male) of S. purpuratus were 1:2.20 (31.3% female) and 1:1.03 (49.2% female) in the 0+ and 1+ y classes, respectively, illustrating the initially higher percentage of males in the butter clam population. From the 2+ y class onward, however, the percentage of females in the population tended to increase with age. The shell length at sexual maturity was analyzed using a logistic regression model, and was determined to be 54.5 and 45.5mmfor females and males, respectively. The gonad index displayed a definitive pattern of seasonal changes, with high values in the spring and fall and low values in the summer and winter for both males and females. The butter clam S. purpuratus was found to have two spawning seasons per year, with the main spawning period being in May–June.

Lee, Y.G.; Kim, S.; Jeong, D.U.; Kim, J.K., and Woo, H.J., 2013. Effects of heavy rainfall on sedimentation in the tidal salt marsh of Suncheon Bay, South Korea. Tide observations, geographic surveys, sediment composition, and sediment accretion rate monitoring were conducted to investigate the relationship between general pattern changes and control factors of the accretion rate at 10 localities of the tidal salt marsh of Suncheon Bay over 2 years (June 2007–May 2009). The substrate sediments of the tidal salt marshes that are distributed between the mean sea level and the high water of ordinary spring tide are mainly composed of silt (37.98%) and clay (60.45%) and have a high average annual accretion rate of 28.88 mm/y. The high substrate sedimentation of tidal salt marshes is caused by: (1) a high concentrated suspended sediment supply from the tidal flat; (2) considerable marsh grass vegetation; (3) undeveloped tidal salt marsh creek; and (4) marsh elevation distributed between the mean sea l...

In this study, the morphology and ultrastructure of the foot of Tegillarca granosa was compared with the bivalves from different habitats. The sediment of habitat of T. granosa is mostly a mixture of sand (68.93%) and mud (24.12%). The foot is wedge-shaped with multiple projections on the surface and covered with ciliary tufts. The epithelial layer is simple and composed of ciliated columnar epithelia and mucous cells. Although the mucous cells are distributed mostly in the epithelial layer, they are developed even in the connective tissues and muscle layers, and the mucous cells mostly contain acidic carboxylated mucosubstances. From the TEM observation, secretory cells are classified into three types. Type A secretory cell has a goblet form and is most widely distributed among the three types. Type B secretory cell has an oval form and the secretory granule has fibrous substance. Type C secretory cell has an elongated elliptic form and membrane-bounded secretory granules. The muscle fiber bundles are composed mainly of smooth muscle fibers. The smooth muscle fibers can be divided into two types. Type A muscle fibers have evenly distributed thick microfilaments between the thin microfilaments of cytoplasm. Type B muscle fiber has cluster of condensed microfilaments in the medulla cytoplasm while the cortical cytoplasm has loose distribution of thin microfilaments.

The shape and microscopic structure of the foot of the equilateral venus, Gomphina Veneriformis are described by light and electron microscopy along with the substrate conditions of their habitat. The habitat sediment of G. veneriformis is composed of sand (2 - 0.063 mm in diameter), mainly. The foot is wedge-shaped with multiple vertical furrows on the surface. Although the foot is composed of an epithelial layer, a connective tissue layer and a muscular layer, the boundary between the connective tissue and muscular layer is not clear. The epithelial layer was composed mostly of ciliated columnar epithelia and secretory cells. Epithelial cells forming the apical region of the fold were long columnar, while cells of the interfold were mostly short columnar. The cilia and microvilli were commonly observed on the free surface of epithelial cells, while tight junctions of apico-lateral aspect and membrane interdigitations were found between the epithelial cells. Secretory cells were found to contain acidic mucopolysaccharide, and were classified into two types in accordance with the shapes and ultrastructures of secretory granules. The muscle fibers were composed of thin and thick microfilaments, the proportions of which were 81.3% and 18.7%, respectively. It was determined that such morphology and structural characteristics of the foot of G. veneriformis would present advantageous conditions for borrowing into substrate and mobility.

To understand the role of depositional processes on the distribution of benthic foraminifera, grain size analysis, paleontological statistics and textural analysis were conducted on three piston cores (Core Nos. 3, 7, 9) from the southeastern Yellow Sea of Korea. Two foraminiferal assemblages were defined by cluster analysis. The Cibicides lobatulus-Ammonia ketienziensis assemblage has low P.F/B.F, species diversity and evenness and high number of benthic foram. individuals/20 ml, and is interpreted as representing relict benthic foraminiferal assemblage comprising the upper layer of Core No. 7 and No. 9. The deposit of well sorted alternation layers of muddy sand and sandy mud in Core No. 9. is interpreted as being influenced by hydraulic sorting processes of higher wave and current especially during storm periods. The preservation of 13 Pseudorotalia gaimardii extracted from Core No. 7 confirmed that bed load transport was responsible for its heavily abraded and broken thick-walled tests. The Pseudoparrellan araensis assemblage is a recent benthic foraminiferal assemblage found in the modern homogeneous fine-grained mud facies corresponding to the uppermost part of HMB. It seemed that the apparent sorting phenomena and bed load transport of the benthic foraminifera are the result of turbidity currents which promulgated by rapid tidal currents formed during the last postglacial period in the southeastern Yellow Sea of Korea.

School of Construction Engineering, Pukyong National University, Busan 608-737, KoreaTo predict changes in the marine environment of the Beolgyo Stream Estuary in Jeonnam Province, South Korea, where cohesive tidal flats cover a broad area and a large bridge is under construction, this study conducted numerical simulations involving tidal flow and cohesive sediment transport. A wetting and drying (WAD) technique for tidal flats from the Princeton Ocean Model (POM) was applied to a large-scale-grid hydrodynamic module capable of evaluating the flow resistance of structures. Derivation of the eddy viscosity coefficient for wakes created by structures was accomplished through the explicit use of shear velocity and Chezy’s average velocity. Furthermore, various field observations, including of tide, tidal flow, suspended sediment concentrations, bottom sediments, and water depth, were performed to verify the model and obtain input data for it. In particular, geologic parameters related to the evaluation of settling velocity and critical shear stresses for erosion and deposition were observed, and numerical tests for the representation of suspended sediment concentrations were performed to determine proper values for the empirical coefficients in the sediment transport module. According to the simulation results, the velocity variation was particularly prominent around the piers in the tidal channel. Erosion occurred mainly along the tidal channels near the piers, where bridge structures reduced the flow cross section, creating strong flow. In contrast, in the rear area of the structure, where the flow was relatively weak due to the formation of eddies, deposition and moderated erosion were predicted. In estuaries and coastal waters, changes in the flow environment caused by artificial structures can produce changes in the sedimentary environment, which in turn can affect the local marine ecosystem. The numerical model proposed in this study will enable systematic prediction of changes to flow and sedimentary environments caused by the construction of artificial structures. Key words: Beolgyo Stream Estuary, Cohesive sediment transport, Erosion and deposition, Flow resistance of structures, Numerical simulation, Tide and tidal flow

In the four sedimentary cores from Yeoja Bay, the analyses of grain size, benthic foraminiferal species compositions, assemblages and statistics were carried out to investigate the effects of late Holocene sea-level change on benthic foraminifera. The core sediments were mainly composed of fine-grained silt and clay. The benthic foraminifera were classified into 27 species of 16 genera, 30 species of 21 genera, 50 species of 29 genera and 52 species of 29 genera in Core YC-1 to 4, respectively. In the result of cluster analysis, it seemed that Group 1 (Core YC-1 and 2) of representative A. beccarii assemblages was deposited in upper bay environment and Group 2 (Core YC-3 and 4) of representative E. clavatum-A. beccarii assemblages was deposited in inner bay environment affected by offshore water. In the result of species composition analysis, the production frequency of A. beccarii was gradually decreased from low layer to upper layer, whereas production frequency of E. clavatum and P.F./T.F. was gradually increased to upward. These change patterns appeared in benthic and planktonic foraminifera seemed to reflect the late Holocene sea-level rise in Yeoja Bay.

An eco-hydrodynamic model was used to estimate the carrying capacity of pollutant loads and response of water quality to environmental change in Yeoja Bay, Korea. An energy-system model also was used to simulate the fluctuation in nutrients and organic matter in the bordering wetland. Most water quality factors showed a pulsed pattern, and the concentrations of nutrients and organic matter of seawater increased when input loads of nutrients increased due to freshwater discharge. The well-developed tidal zones and wetlands in the northern area of the bay were highly sensitive to input loads. Residence times of water, chemical oxygen demand (COD), and dissolved inorganic nitrogen (DIN) within the bay were estimated to be about 16 days, 43.2 days, and 50.2 days, respectively. Water quality reacted more sensitively to the effects of nitrogen and phosphorus input than to COD. A plan to reduce the present levels of COD and dissolved inorganic phosphorus (DIP) by 20–30% and DIN by at least 50% in pollutant loads is needed for satisfying the target water quality criteria. The natural removal rate of nutrients in wetlands by reeds was assessed to be approximately 10%.

Seawater monitoring and geochemical and benthic foraminiferal analysis of sediments were conducted to identify the effects of hypoxia created by a mussel farm on benthic foraminifera in a semi-closed bay. Extremely polluted reductive conditions with a high content of organic matter (OM) at12.0% and oxygen minimum zones (OMZs) with dissolved oxygen (DO)0.4mg∙L(-1) were formed below the mussel farm in the northwest area of Gamak Bay, and gradually diffused toward the south. Highly similar patterns of variation were observed in species diversity, abundance frequency, and benthic foraminiferal assemblage distributed from Elphidium subarcticum-Ammonia beccarii in the northwest area through E. subarcticum-A. beccarii-Trochammina hadai, E. subarcticum-A. beccarii-Elphidiumclavatum, and E. clavatum-Ammonia ketienziensis in the southern area. These phenomena were caused by hydrodynamics in the current water mass. It was thought that E. subarcticum is a bioindicator of organic pollution caused by the mussel farm.

Smaragdina nipponensis (Chujo) (Coleoptera: Chrysomelidae) 1951 is recorded in Korea for the first time. A description, a modified key to the Korean Smaragdina, photographs of adults, and illustrations of diagnostic characteristics are provided.

To estimate of the dispersion trend of 3H and 14C discharged from the Wolsung Nuclear Power Plants, the present level of 3H and 14C in environmental samples in the vicinity of the Wolsong site was studied. Tree-ring cellulose analyses were carried out for retrospective evaluation of 3H and 14C in the environment around the Wolsong Nuclear Power Plants. 3H released from the Wolsong Nuclear Power Plants has affected an area up to a 25-km radius from the site, while almost all 14C was deposited within a 2-km radius, reaching to a natural level over 2 km. Organically bound tritium concentrations in tree rings were strongly correlated with the gaseous tritium discharge rate, while delta14C (excess) in tree rings ranged from 204 per thousand to 460 per thousand, which did not significantly vary with year.

大韓民国南東部浦項地域に分布する中新統の古環境を, 底生有孔虫群集に基づき解析した.Qモード主成分分析の結果, 第1主成分は各底生有孔虫種の産出頻度, 第2主成分は海水の炭酸カルシウム濃度, 第3主成分は沿岸水の影響の程度, 第4主成分は中層水と深層水, 第5主成分は寒流系水塊の影響, 第6主成分は中層水と表層水に関係している.主成分分析の結果と現在の西南日本沖太平洋の海洋環境から, 中新統の堆積環境を推定した.北部地域のHeunghae層は中部漸深海帯下部で堆積した.中部地域のCheongogsa層中部の堆積深度は上部漸深海帯から中部漸深海帯上部であった.Cheongogsa層最上部は中部漸深海帯下部に, Hagjeon層は上部漸深海帯から中部漸深海帯上部で堆積した.Duho層下部の古水深は上部漸深海帯から中部漸深海帯下部である.南部地域に分布するHagjeon層は上部漸深海帯から中部漸深海帯上部にて堆積し, 中部漸深海帯下部まで深くなったこともあった.Cheongogsa層中部(N 8帯)以降, 寒流系水塊の影響が認められた.

Tributyltin (TBT) is the most common pesticide in marine and freshwater environments. To evaluate the potential ecological risk posed by TBT, we measured biological responses such as growth rate, gonad index, sex ratio, the percentage of intersex gonads, filtration rate, and gill abnormalities in the equilateral venus clam (Gomphina veneriformis). Additionally, the biochemical and molecular responses were evaluated in G. veneriformis exposed to various concentrations of TBT. The growth of G. veneriformis was significantly delayed in a dose-dependent manner after exposure to all tested TBT concentrations. After TBT was administered to G. veneriformis, the gonad index decreased and the sex balance was altered. The percentage of intersex gonads also increased significantly in treated females, whereas no intersex gonads were detected in the solvent control group. Additionally, intersex gonads were detected in male G. veneriformis specimens exposed to relatively high TBT concentrations (20 μg L⁻¹). The filtration rate was also reduced in a dose-dependent manner in TBT-exposed G. veneriformis. We also noted abnormal gill morphology in TBT-exposed G. veneriformis. Furthermore, increases in antioxidant enzyme activities were observed in TBT-exposed G. veneriformis clams, regardless of dosage. Vitellogenin gene expression also increased significantly in a dose-dependent manner in G. veneriformis exposed to TBT. These results provide valuable information regarding our understanding of the toxicology of TBT in G. veneriformis. Moreover, the responses of biological and molecular factors could be utilized as information for risk assessments and marine monitoring of TBT toxicity.